As is well known, a memory card basically comprises a card body of substantially rectangular shape, made from a plastic material, and an electronic module fixed to the card body, this electronic module being formed basically by a support part and by a semiconductor chip fixed to the support part.
More particularly, the support part has electric contacts on its outer face, for making contact with the connector of the card reader, and has on its other face a semiconductor chip electrically connected to conductive regions of the support part, for example by conductive wires. Usually the assembly formed by the semiconductor chip and the conductive wires is encapsulated in an insulating material for mechanical protection and electrical insulation.
Memory cards have to adhere to various characteristics defined by very precise standards, such as ISO 7810. Among the specifications imposed on cards, the first lies in that the thickness of the card has to be within very tight tolerances around the value of 0.8 mm. In consequence, it is necessary for the electronic module to have a very small thickness, so that it can be fixed in the card body. A second specification lies in that the card fitted with its electronic module should satisfy bending and twisting tests. It is accordingly necessary for the electronic module to be fixed properly if it is not to become detached under the action of twisting or bending, and it is moreover necessary for the electronic module itself to have such good mechanical properties that it does not run the risk of being itself destroyed when bending and twisting stresses are applied.
Among the electronic cards manufactured at present, a large number are referred to as disposable, that is to say that when data stored in the memory circuits of the integrated circuits implemented in the electronic module of the card has been used, new data cannot be loaded into the memory circuits and, therefore, the card becomes useless. This is typically the case with memory cards serving as telephone pre-payment cards. It will be understood that, in this case, it is necessary that the cost of manufacture of the card should be as low as possible, so that the manufacturing cost only represents a small percentage of the overall selling price of the card supplied to the user, this sale price essentially including the total services to which the user will be entitled in making use of the card.
The support part of the electronic module is most often formed in existing cards by means of a printed circuit, of which the external metal layer is etched to define the various external contact areas of the card. However, this technique is relatively costly. For this reason it has already been proposed in European patent application EP 0 254 640 to make the support part by means of a lead-frame.
According to the technique described in the European application cited above, a succession of patterns is formed in a conductive metal strip, each pattern corresponding to the creation of one electronic module. The various external electrical contact areas are separated from one another by cutting, the conductor parts thus obtained remaining connected mechanically to the remainder of the metal strip by bridges of small dimensions. In a first stage the semiconductor chip is fixed on one of the conductor parts; then the encapsulation of the semiconductor chip follows, in order to protect the chip and to effect an insulating mechanical connection between the ends of the conductor parts. The bridges merely then have to be cut to obtain an electronic module.
An object of the present invention is to provide a method of making an electronic module for a memory card, also using the lead-frame technique but allowing use of a thinner lead-frame, while still ensuring an even better mechanical bond between the conductor parts.